Start everyone at their current MMR or the lowest division for the League that they're in currently, from Dynamic Queue, in Solo Queue.
What you're doing by delaying this is effectively giving Solo Queue absolutely no chance for success. People like myself, who would much rather be playing Solo than Dynamic, are now incentivized to not even play it since it's being released so late. We already started our climb. We'll have to start all over, way back down in ranking, and it's because of you guys.
It's unfortunate that this even has to be considered, since rankings will be skewed, but at least we can hope pure solo will correct and fix them as time goes on.
**Spoiler:** They aren't going to do this, the people who want to enjoy Solo Queue will be stressed by having to restart and not do it, and Riot will say, "We told you so! No one even liked Solo Queue!" and it will disappear completely.